What are the benefits and risks of light therapy for treating atopic eczema (also known as eczema or atopic dermatitis)?

Key messages

Narrowband (NB) ultraviolet B (UVB), compared to placebo (a sham treatment), may improve eczema severity (including itch) and may not affect the number of people leaving a study because of unwanted effects.

We were unable to confidently draw conclusions for other phototherapy (light therapy) treatments.

Future research needs to assess longer term effectiveness and safety of NB-UVB and other forms of phototherapy for eczema.

What is eczema?

Eczema is a condition that results in dry, itchy patches of inflamed skin. Eczema typically starts in childhood, but can improve with age. Eczema is caused by a combination of genetics and environmental factors, which lead to skin barrier dysfunction. Eczema can negatively impact quality of life, and the societal cost is significant.

How is eczema treated?

Eczema treatments are often creams or ointments that reduce itch and redness, applied directly to the skin. If these are unsuccessful, systemic medicines that affect the whole body, or phototherapy are options. Phototherapy can be UVB, ultraviolet A (UVA), or photochemotherapy (PUVA), where phototherapy is given alongside substances that increase sensitivity to UV light.

What did we want to find out?

We wanted to find out whether phototherapy was better than no treatment or other types of treatment for treating eczema, and whether it caused unwanted effects.

What did we do?

We searched for studies that investigated phototherapy compared with no treatment, placebo, other forms of phototherapy, or another type of eczema treatment. Studies could include people of all ages, who had eczema diagnosed by a healthcare professional.

We compared and summarised the results of the studies, and rated our confidence in the evidence.

What did we find?

We found 32 studies, involving 1219 people with eczema (average age: 28 years), who were recruited from dermatology clinics. Most studies assessed people with skin type II to III (which is classed as white to medium skin colour), and moderate to severe eczema, with which they had lived for many years. Studies included similar numbers of males and females.

The studies were conducted in Europe, Asia, and Egypt (setting was not reported by seven studies), and lasted, on average, for 13 weeks. Almost half of the studies reported their source of funding; two were linked to commercial sponsors.

Our included studies mostly assessed NB-UVB, followed by UVA1, then broadband ultraviolet B; fewer studies investigated other types of phototherapy. The studies compared these treatments to placebo, or no treatment, another type of phototherapy, different doses of the same sort of phototherapy, or other eczema treatments applied to the skin or taken by tablet.

None of the studies investigated excimer lamp (a source of UV radiation) or heliotherapy (the use of natural sunlight), that were other light therapies in which we were interested.

What are the main results of our review?

When compared to placebo, NB-UVB may:

- improve signs of eczema assessed by a healthcare professional (1 study, 41 people);

- increase the number of people reporting less severe itching (1 study, 41 people);

- increase the number of people reporting moderate or greater improvement of eczema, measured by the Investigator Global Assessment scale (IGA), a 5-point scale that measures improvement in eczema symptoms (1 study, 40 people); and

- have no effect on the rate of people withdrawing from treatment due to unwanted effects (3 studies, 89 people).

None of the studies assessing NB-UVB against placebo measured health-related quality of life.

We do not know if NB-UVB (compared with UVA1 or PUVA) or UVA1 (compared with PUVA) has an effect on the following:

- signs of eczema assessed by a healthcare professional;

- patient-reported eczema symptoms;

- IGA;

- health-related quality of life; and

- withdrawals due to unwanted effects.

This is because either we are not confident in the evidence, or they were not reported.

We did not identify any studies that investigated UVA1 or PUVA compared with no treatment.

Some studies reported that phototherapy caused some unwanted effects, including skin reactions or irritation, UV burn, worsening of eczema, and skin infections. However, these did not occur in most people.

What are the limitations of the evidence?

Our confidence in the evidence is limited, mainly because only a few studies could be included in each comparison, and the studies generally involved only small numbers of people.

How up to date is this evidence?

The evidence is up to date to January 2021.

Authors' conclusions: 

Compared to placebo or no treatment, NB-UVB may improve physician-rated signs, patient-reported symptoms, and IGA after 12 weeks, without a difference in withdrawal due to adverse events. Evidence for UVA1 compared to NB-UVB or PUVA, and NB-UVB compared to PUVA was very low certainty. More information is needed on the safety and effectiveness of all aspects of phototherapy for treating AE.

Read the full abstract...

Atopic eczema (AE), also known as atopic dermatitis, is a chronic inflammatory skin condition that causes significant burden. Phototherapy is sometimes used to treat AE when topical treatments, such as corticosteroids, are insufficient or poorly tolerated.


To assess the effects of phototherapy for treating AE.

Search strategy: 

We searched the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase, and ClinicalTrials.gov to January 2021.

Selection criteria: 

We included randomised controlled trials in adults or children with any subtype or severity of clinically diagnosed AE. Eligible comparisons were any type of phototherapy versus other forms of phototherapy or any other treatment, including placebo or no treatment.

Data collection and analysis: 

We used standard Cochrane methodology. For key findings, we used RoB 2.0 to assess bias, and GRADE to assess certainty of the evidence. Primary outcomes were physician-assessed signs and patient-reported symptoms. Secondary outcomes were Investigator Global Assessment (IGA), health-related quality of life (HRQoL), safety (measured as withdrawals due to adverse events), and long-term control.

Main results: 

We included 32 trials with 1219 randomised participants, aged 5 to 83 years (mean: 28 years), with an equal number of males and females. Participants were recruited mainly from secondary care dermatology clinics, and study duration was, on average, 13 weeks (range: 10 days to one year). We assessed risk of bias for all key outcomes as having some concerns or high risk, due to missing data, inappropriate analysis, or insufficient information to assess selective reporting.

Assessed interventions included: narrowband ultraviolet B (NB-UVB; 13 trials), ultraviolet A1 (UVA1; 6 trials), broadband ultraviolet B (BB-UVB; 5 trials), ultraviolet AB (UVAB; 2 trials), psoralen plus ultraviolet A (PUVA; 2 trials), ultraviolet A (UVA; 1 trial), unspecified ultraviolet B (UVB; 1 trial), full spectrum light (1 trial), Saalmann selective ultraviolet phototherapy (SUP) cabin (1 trial), saltwater bath plus UVB (balneophototherapy; 1 trial), and excimer laser (1 trial). Comparators included placebo, no treatment, another phototherapy, topical treatment, or alternative doses of the same treatment.

Results for key comparisons are summarised (for scales, lower scores are better):

NB-UVB versus placebo/no treatment

There may be a larger reduction in physician-assessed signs with NB-UVB compared to placebo after 12 weeks of treatment (mean difference (MD) -9.4, 95% confidence interval (CI) -3.62 to -15.18; 1 trial, 41 participants; scale: 0 to 90). Two trials reported little difference between NB-UVB and no treatment (37 participants, four to six weeks of treatment); another reported improved signs with NB-UVB versus no treatment (11 participants, nine weeks of treatment).

NB-UVB may increase the number of people reporting reduced itch after 12 weeks of treatment compared to placebo (risk ratio (RR) 1.72, 95% CI 1.10 to 2.69; 1 trial, 40 participants). Another trial reported very little difference in itch severity with NB-UVB (25 participants, four weeks of treatment).

The number of participants with moderate to greater global improvement may be higher with NB-UVB than placebo after 12 weeks of treatment (RR 2.81, 95% CI 1.10 to 7.17; 1 trial, 41 participants).

NB-UVB may not affect rates of withdrawal due to adverse events. No withdrawals were reported in one trial of NB-UVB versus placebo (18 participants, nine weeks of treatment). In two trials of NB-UVB versus no treatment, each reported one withdrawal per group (71 participants, 8 to 12 weeks of treatment).

We judged that all reported outcomes were supported with low-certainty evidence, due to risk of bias and imprecision. No trials reported HRQoL.

NB-UVB versus UVA1

We judged the evidence for NB-UVB compared to UVA1 to be very low certainty for all outcomes, due to risk of bias and imprecision. There was no evidence of a difference in physician-assessed signs after six weeks (MD -2.00, 95% CI -8.41 to 4.41; 1 trial, 46 participants; scale: 0 to 108), or patient-reported itch after six weeks (MD 0.3, 95% CI -1.07 to 1.67; 1 trial, 46 participants; scale: 0 to 10). Two split-body trials (20 participants, 40 sides) also measured these outcomes, using different scales at seven to eight weeks; they reported lower scores with NB-UVB. One trial reported HRQoL at six weeks (MD 2.9, 95% CI -9.57 to 15.37; 1 trial, 46 participants; scale: 30 to 150). One split-body trial reported no withdrawals due to adverse events over 12 weeks (13 participants). No trials reported IGA.

NB-UVB versus PUVA

We judged the evidence for NB-UVB compared to PUVA (8-methoxypsoralen in bath plus UVA) to be very low certainty for all reported outcomes, due to risk of bias and imprecision. There was no evidence of a difference in physician-assessed signs after six weeks (64.1% reduction with NB-UVB versus 65.7% reduction with PUVA; 1 trial, 10 participants, 20 sides). There was no evidence of a difference in marked improvement or complete remission after six weeks (odds ratio (OR) 1.00, 95% CI 0.13 to 7.89; 1 trial, 9/10 participants with both treatments). One split-body trial reported no withdrawals due to adverse events in 10 participants over six weeks. The trials did not report patient-reported symptoms or HRQoL.

UVA1 versus PUVA

There was very low-certainty evidence, due to serious risk of bias and imprecision, that PUVA (oral 5-methoxypsoralen plus UVA) reduced physician-assessed signs more than UVA1 after three weeks (MD 11.3, 95% CI -0.21 to 22.81; 1 trial, 40 participants; scale: 0 to 103). The trial did not report patient-reported symptoms, IGA, HRQoL, or withdrawals due to adverse events.

There were no eligible trials for the key comparisons of UVA1 or PUVA compared with no treatment.

Adverse events

Reported adverse events included low rates of phototoxic reaction, severe irritation, UV burn, bacterial superinfection, disease exacerbation, and eczema herpeticum.